Define a capsule mete-data struct which can be declared globally
per-proxy to allow libcapsule to manage a set of capsules and
merge them into one namespace if they share a /host prefix.

This allows us to have one capsule per proxied library, each
with the correct soname instead of one monolithic blob capsule
which can only have one soname.

Conflicts:
	capsule/capsule-dlmopen.c
	capsule/capsule-init.c
	capsule/capsule-wrappers.c